cookyman Posted May 25, 2004 Report Posted May 25, 2004 i have bee lookin around and asking people i know about this very interesting topic. i have heard that the speed of lite is slowing down. i just wanted to know whether this is true. i have evidence backing this up but i still want to check with u guys. for example it was said that back in 1700's it was i few 100 kms faster that it is know.
Tormod Posted May 25, 2004 Report Posted May 25, 2004 Hi cookyman, welcome. I would be very interested in this evidence. Recent research (over many years by Paul Davies, John Barrow et al) has shown that the speed of light may have slowed down over billions of years, since the expansion rate of the universe seems to be accelerating. The speed of light would not change over a few centuries. It is a fundamental constant in nature and would not change all of a sudden without it having major implications on things. However, this has been refuted by, among others, NASA:http://www.space.com/scienceastronomy/lightspeed_031217.html And please - if you have "evidence" don't claim to have it and not post it. Read our FAQ. With regards,Tormod
cookyman Posted May 25, 2004 Author Report Posted May 25, 2004 ok... sry bout not posting any evidence but i have it here. a few years ago.. i can't remember the scientists names but they where from melbournin australia. but anyway they decided to do a test on the speed of light and looked at sum records of a french scientist from the 1700's (can't remember his name) about the speed of light and his measurements of it and he found that they where suposedly incorent with the measurements form the tests that are run today in the magnetic ring thing ova in US (sry but can't remember the name of it but its a huge electromagnetic ring that shoot atoms or electrons or something) anyway they did sume tests with the equipment that was used back in the 1700's that had been kept inmuseaums over europe and foundthatunder exactly the same conditions the speed of light measured from the old equipment was exactly the same as what the speed of light is measured as now in the elctro magnetic rings. so that was the evidence... lol. sounds pretty vauge but that is wat i was told so it does sound a little unbeliveable hey. oh well tell me ur opions plz. PS. thnx for the site. and thnx for those names.. lol Cookyman
Tormod Posted May 25, 2004 Report Posted May 25, 2004 cooky, that is not evidence but hearsay! First of all, measurements of the speed of light in the 1700's cannot possibly have been accurate to the 100s of kilometers due to the lack of tools. However, Ole Roemer measured the speed of light in 1676 by famously observing the eclipse of Io by Jupiter. However, he did not know the exact distance between Earth and Jupiter and his calculations were wrong at 200,000 kilometers per second (although remarkable at the time). The Australian scientists you are referring to might be the team led by Paul Davies. Here is a link:http://aca.mq.edu.au/News/lightspeed.html Another interesting link for background:http://www.museum.vic.gov.au/scidiscovery/light/speed.asp Tormod
cookyman Posted May 25, 2004 Author Report Posted May 25, 2004 lol.. i thought that it sounded a bit unbliveable but anyway... thanks for clearing it up.. i just thought it woulda been interestin if it was true. oh well my science teacher wont be happy..lol thnx for clearing it up Cookyman
Tormod Posted May 25, 2004 Report Posted May 25, 2004 No problem, we like making science teachers unhappy. Tormod
CD27 Posted June 4, 2004 Report Posted June 4, 2004 well, is lite "light"? or did you simply mispell the word? anyways, i will answer the question using the reference frame of "light" exactly. first of all, space is an object, it is not just some simple vast place of "nothingness". we'll call it the aether, since that is what it is usually called anyways. it has been proven that when light passes through a more dense object its speed slows down until it exits that greater desity. the only possibly way that somene could even measure the exact speed of light is if it measured it in an absolutely zero dense object. since space is an object, it has some density, but very little, and because there is no absolutely zero dense object, there is no possible way for us to ever know how fast light really moves. and to say that you can test how fast light is and to conclude that it is becoming slower, well, i wouldn't bet on that. because that could simply mean that everything is becoming a bit more dense on this planet for some reason. and if that is so, we would never really be able to test it, because EVERYTHING ould become more dense, basically meaning that the planet itself is probably getting denser. but not by very much, or we'd notice it then right? lol. but that was a very good question.
Tormod Posted June 4, 2004 Report Posted June 4, 2004 CD27, welcome - There are many ways to measure the exact speed of light, both in vacuum and in physical objects like gases and fluids. I'm curious - why do you question this? Space is not an "object" per se. According to quantum physics space may not even be continous. The speed of light in vacuum has no relation to the density of our planet. We are talking about the finite speed of light as a universal constant, not the speed of light in an object. As you point out, the speed of light is slower when the light passes through, say, gas and water. But that the speed of light currently has a limit of about 300,000 kilometers per second is easily observable. If the speed of light was infinite, then we would instantly see things that happen on distant planets, for example. You could communicate instantly between Earth and a planet at Alpha Centauri. But we see the light from Alpha Centauri as it was 4 years ago. That is why the definition "Light year" is a measure of distance, not time. And, by the way, the aether theory died long ago. Tormod
Anthony Posted June 4, 2004 Report Posted June 4, 2004 Hi all A question for those with difinitive proof or knowledge does light of different frequencies travel at different speeds? Ananog
Tim_Lou Posted June 4, 2004 Report Posted June 4, 2004 frequency*wavelength=C they all have same speed. :-)
Tormod Posted June 4, 2004 Report Posted June 4, 2004 Anthony, you want marshmallows with that? http://www.physics.umd.edu/ripe/icpe/newsletters/n34/marshmal.htm Tormod
CD27 Posted June 7, 2004 Report Posted June 7, 2004 anthony, frequency simply means how many crest or troughs pass in a certain amount of time. if the amplitude of a wave is shorter, then it seems to move faster, but really, the wave is traveling at the same speed of all other waves. the only time a wave would seem to be faster than another is if you took the wave and straitened it to a strait line and compared it to another, both still keeping their frequency speeds. the one with a higher frequency (which is now a strait line) will in fact move faster than the one with a lower frequency..however, it is impossible to make a wave "straiten", or, well, improbable, never impossible. until one day someone finally straitens a wave then i guess light speed will stay the same and everything will be "thought" to be correct. personaly, to me, i think of it as always being wrong, and look for an alternative, if i can't find one, then i accept it and go on with my life, but if i can find evena hint that there is an alternative, it is wrong.
Bo Posted June 8, 2004 Report Posted June 8, 2004 The constant speed of light has nothing to do with the structure or density of spacetime as was proposed before. It is only dependent of some fundamental constants that determine the properties of an electromagnetic field. However there are some measurements done (J.K. Webb et al, Phys rev letters 87) thet the strength of the EM force weakens about one part in 10^16 per year... (this article isn't completely excepted however...)So these days the measurements of fundamental constants in the early universe become a possibility, but it will take some 10 years or so, before we can realy say if they're constant or not. Bo
Freethinker Posted June 8, 2004 Report Posted June 8, 2004 In researching an answer to the question I found some new propositions that suggest that the speed of light IS dependant on the wavelength/ Freq. http://www.aip.org/pnu/1999/split/pnu432-2.htm THE SPEED OF LIGHT IS INDEPENDENT OF FREQUENCY within a factor of 6x10-21. Bradley Schaefer of Yale (203-432-3806, [email protected]) bases this estimate on the observed arrival of gamma rays from distant explosive events in the cosmos, such as gamma-ray bursters. If the speed of light © were slightly different for the different frequency ranges, then some light waves would show up before the others, but this is not the case. The best previous effort to locate a frequency dependency for c, deduced from light coming from the Crab pulsar, was at the 5x10-17 level. Why would c vary with frequency? Einstein's theory of relativity, and its insistence on a universal light speed, might be at fault. Or photons might have mass. Schaefer*s analysis addresses this issue, and puts an upper limit of 10-44 g on any putative photon mass, not quite as sharp a limit as those based on the observed strength of the galactic magnetic field (a nonzero photon mass would allow the fields to decay away). The new sharper limits on any possible frequency-dependency for c is a vindication of relativity. By the way, the prefix for anything as small as 10-21 is "zepto" (Shaefer, Physical Review Letters, 21 June; journalists can obtain the article from AIP.)
nemo Posted August 8, 2004 Report Posted August 8, 2004 Very interesting... I am still curious about the question in this topic's summary. Is light slowing down? I've read about work done by Barry Setterfield from his site and others: http://www.setterfield.org/scipubl.htmlhttp://www.ldolphin.org/bowden.html I am new to this site, but I have done some reading on the other topics - I'd like to discuss the mathematics and scientific theory involved, rather than the fact that Mr. Seterfield happens to have apparently strong religious beliefs posted elsewhere on his site. Is light actually slowing down? Are the measurements taken a few hundred years ago too inacurate to use? Is the idea of challenging c too uncomfortable? Is Mr. Setterfield in need of a user's guide for his calculator?
paultrr Posted November 22, 2004 Report Posted November 22, 2004 The only two feasable choices are: 1.) It is slowing down. 2.) In general since the inflation period it has stayed constant. The answer choice here rather depends upon one's cosmology and who's evidence one accepts. But within the confines of known theory and observational evidence these are the only two possible answers. VSL based cosmology tends to support the first answer irrespective of weither one follows normal GR, PV, etc. The Standard modeling tends to support the second choice. At the current time the only aspect that seems to have changed is the fine structure constant if any. The amount of change over some 14 billion years is very small even if one accepts the evidence as valid. See: http://doc.cern.ch//archive/electronic/other/ext/ext-2004-109.pdf and http://doc.cern.ch//archive/electronic/other/ext/ext-2004-115.pdf andhttp://doc.cern.ch//archive/electronic/other/ext/ext-2004-116.pdf andhttp://doc.cern.ch//archive/electronic/other/ext/ext-2004-121.pdf for a general treatment using one VSL approach. Some of the actual evidence for a constant speed of light comes from research on the breaking of Lorentz invariance. To date that evidence is not conclusive. However, if it has varied it has only varied from T+300000 years to present by a very small amount.
DivineNathicana Posted November 23, 2004 Report Posted November 23, 2004 Wow! I've never heard anything about this postulate. Could it be that the stretching fabric of space-time (post-Big-Bang if it truly occurred) requires light to travel greater distances than before, but its actual speed is still constant? Like, as I understand it, the Big Bang model says that galaxies are not so much moving away from a central point, but are rather staying fixed on a stretching space-time (which is considered vacuum). So then why shouldn't light take a greater amount of time to traverse this ever-increasing uhhh "length" of space-time? Sorry, Tormod, but I don't have any evidence for this as it is more of a spur-of-the-moment question rather than an actual theory (as far as I know). - Alisa
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